A Load-Haul-Dump vehicle (LHD) is a mid-sized underground mining vehicle, typically up to about 60 tonnes in weight. A LHD is often used to load, haul and dump broken cuttings or ore from an open stope to a crusher or waiting truck to be transported to the surface. A LHD has wheels which are laterally fixed, and instead effects steering by way of an articulation in the chassis between front and rear axles, controlled by hydraulic steering cylinders or the like.
In coal mines, restricted roof heights demand custom designed machinery to fit the confines of the mine heading. The mine heading height is set by the coal seam height. Soft rock coal cutting machines have limited ability to cut roof or floor stone. Typical heading height in Australian seams (for example) ranges from 1800 mm to 3500 mm. Often mine services such as piping, cabling, and conveyor structures further restrict the available travelling height clearances. Old workings or restricted drift or cage access can also limit machine size. Similar height constraints often apply in mines other than coal mines.
A conventional surface loader typically has an engine directly coupled to a torque converter/transmission, with drop box to prop shaft output to axles. In this arrangement the engine and drive train are positioned above the axle as there is no pressing restriction on vehicle height. The cabin is centrally located on top of the transmission, with a forward facing seat. This layout is not possible for an underground coal application.
Underground mining vehicles have distinct design requirements to meet the demands and constraints of the underground mining environment. Size is one such constraint. The tasks of a LHD also require high traction, so that underground LHDs invariably provide drive to all four wheels and thus have a drive shaft across the articulation, and also generally require a traction aiding device in addition to a differential on each of the front and rear axles.
In contrast to surface loaders, typical underground machines have a low positioned engine, positioned aft of the rear axle, with a transfer box to lift the drive line over the rear axle. FIG. 1 shows a drive train of one such previous type of underground LHD. Power from a diesel engine 3 (only partially shown) is passed via a step box 7 and transfer shaft 8 to a power-shift transmission 4. The transmission passes power to the rear axle 5 via rear drive shaft 9. Power passes to the front axle 6 via front drive shaft 10, which is articulated in order to pass the central articulation of the LHD vehicle.
As can be seen, in the drive train of FIG. 1 the transmission 4 is positioned in front of the rear axle 5, with a drop to prop shaft output to the drive shafts 9 and 10. This configuration in practice necessitates that the driver cabin 202 must be located to one side of the machine, in front of one of the rear wheels, as shown in FIG. 2. This is disadvantageous at least because access to the driver's cabin is via the articulation zone 204 of the machine. Because of the significant amount of reversing the LHD can be required to perform, LHDs of the type shown in FIG. 2 are sometimes configured so that the operator's seat is facing across the vehicle; and in such arrangements the driver must spend a significant amount of time with head turned, predominantly to one side.
In particular the articulation area 204 of the machine is known to be a dangerous area due to the pinch point crush hazard. Conventional LHDs having the cabin door opening into the articulation area attempt to mitigate this risk by providing controls which improve safe access to the driver's cabin. Nevertheless, with accumulator reserve steering, and the risk of the steering wheel being used as a handle to enter or exit the driver's cabin, there remains a hazard that the machine will articulate and crush the driver on entry to the machine.
Conventional LHDs also require that the driver must spend a significant time with head turned to the left or right, for example due to the placement of the cabin 202, which can cause fatigue, discomfort and even postural injury.
A further issue is that LHD machines are, due to their role, subjected to considerable demand on brakes. This often causes premature brake wear, requiring costly downtime for brake changes. As enclosed oil immersed brakes are typically used in such a heavy duty axle design, the brakes can only be changed with axle disassembly which involves considerable time and cost.
Other underground vehicles, such as chock carriers, have significantly different operating requirements, such as mobility and traction requirements.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.